# Mu2 Octantis

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**Mu2 Octantis** (μ2 Oct) is a [binary star](/source/Binary_star) system in the constellation [Octans](/source/Octans), whose primary and secondary stars have [apparent magnitudes](/source/Apparent_magnitude) of +6.481 and 7.153, respectively.[1] Based on [parallax](/source/Parallax) measurements, it lies 130.3 [light-years](/source/Light-year) away.[2][3]

The two stars, HD 196067 and HD 196068 (also named μ2 Oct A and μ2 Oct B), are separated at 17 arcseconds in the sky, corresponding to 740 [astronomical units](/source/Astronomical_unit) (AU). The semimajor axis of the stars' orbit is 932 AU.[4]

Component A is a [G-dwarf](/source/G-dwarf) star with 1.33 and 1.73 times of the [Sun's mass](/source/Sun's_mass) and [radius](/source/Solar_radius), respectively. Component B also a G-type [main-sequence](/source/Main-sequence) star with a radius 1.19 times larger than the Sun. Their [effective temperatures](/source/Effective_temperature) are similar. HD 196068 has a higher [metallicity](/source/Metallicity) than its companion, the reasons for this are uncertain.[5]

## Planetary system

From 1998 to 2012, the system was observed using the [CORALIE](/source/CORALIE) instrument, at the [ESO](/source/ESO)'s [La Silla Observatory](/source/La_Silla_Observatory).[4]

In November 2012, a long-period, wide-orbiting [planet](/source/Extrasolar_planet) was deduced by [radial velocity](/source/Radial_velocity) around HD 196067. The planet has been pulled to an eccentric orbit by the B star HD 196068. The planet's true mass, as measured by [astrometry](/source/Astrometry), is , placing it right on the traditionally adopted boundary between planets and [brown dwarfs](/source/Brown_dwarf).[6]

A second, innermost planet was detected using [radial velocity](/source/Radial_velocity) observations with the CORALIE, [HARPS](/source/HARPS), and [ESPRESSO](/source/ESPRESSO) observatories. Despite its small orbit, it does not [transit](/source/Astronomical_transit) the host star.[7]

## References

1. Paunzen, E. (2015-08-01). "A new catalogue of Strömgren-Crawford uvbyβ photometry". *Astronomy and Astrophysics*. **580**: A23. [arXiv:1506.04568](https://arxiv.org/abs/1506.04568). [Bibcode:2015A&A...580A..23P](https://ui.adsabs.harvard.edu/abs/2015A%26A...580A..23P). [doi:10.1051/0004-6361/201526413](https://doi.org/10.1051/0004-6361/201526413). [ISSN 0004-6361](https://www.worldcat.org/issn/0004-6361)

1. Marmier, M. et al. (2013). "The CORALIE survey for southern extrasolar planets XVII. New and updated long period and massive planets". *Astronomy and Astrophysics*. **551**: A90. [arXiv:1211.6444](https://arxiv.org/abs/1211.6444). [Bibcode:2013A&A...551A..90M](https://ui.adsabs.harvard.edu/abs/2013A%26A...551A..90M). [doi:10.1051/0004-6361/201219639](https://doi.org/10.1051/0004-6361/201219639). [S2CID 59467665](https://api.semanticscholar.org/CorpusID:59467665)

1. Flores, M; Yana Galarza, J; Miquelarena, P; Saffe, C; Jaque Arancibia, M; Ibañez Bustos, R V; Jofré, E; Alacoria, J; Gunella, F (2023-12-06). "Elemental abundance differences in the massive planet-hosting wide binary HD 196067−68". *Monthly Notices of the Royal Astronomical Society*. **527** (4): 10016–10024. [arXiv:2311.17272](https://arxiv.org/abs/2311.17272). [doi:10.1093/mnras/stad3714](https://doi.org/10.1093/mnras/stad3714). [ISSN 0035-8711](https://www.worldcat.org/issn/0035-8711)

1. Li, Yiting; Brandt, Timothy D.; Brandt, G. Mirek; Dupuy, Trent J.; Michalik, Daniel; Jensen-Clem, Rebecca; Zeng, Yunlin; Faherty, Jacqueline; Mitra, Elena L. (2021). "Precise Masses and Orbits for Nine Radial-velocity Exoplanets". *The Astronomical Journal*. **162** (6): 266. [arXiv:2109.10422](https://arxiv.org/abs/2109.10422). [Bibcode:2021AJ....162..266L](https://ui.adsabs.harvard.edu/abs/2021AJ....162..266L). [doi:10.3847/1538-3881/ac27ab](https://doi.org/10.3847/1538-3881/ac27ab). [S2CID 237592581](https://api.semanticscholar.org/CorpusID:237592581)

1. Delisle, J.-B.; Faria, J. P.; Ségransan, D.; Fontanet, E.; Ceva, W.; Barbato, D.; Sousa, S. G.; Unger, N.; Leleu, A. (2025-09-30). "Architecture of planetary systems with and without outer giant planets I. Inner planet detections around HD 23079, HD 196067, and HD 86226". *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. [arXiv:2509.26232](https://arxiv.org/abs/2509.26232)

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Adapted from the Wikipedia article [Mu2 Octantis](https://en.wikipedia.org/wiki/Mu2_Octantis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Mu2_Octantis?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.